Making a Determination of Driver Impairment

An arrest for driving under the influence starts with a reasonable suspicion on the part of the officer. Maybe he or she noticed you slurring your words when pulled over for running a stop sign, or maybe the officer made the initial stop because you were driving erratically. The officer has the right to conduct a limited investigation to confirm the suspicion of impairment.

Because of the tools available, it is easier to make the determination if you are impaired by alcohol than by other drugs. Determining if you are under the influence of the latter can be more difficult and sometimes requires the involvement of a specially trained officer called a Drug Recognition Expert.

Chemical Testing

Chemical testing involves obtaining a sample from your body and checking for the presence of alcohol or other drugs. Testing for intoxicating substances may involve screening your breath, urine, or blood. Breath testing is common to confirm or rule out the presence of alcohol because the test is relatively easy to administer. However, breath tests only screen for alcohol, not other substances, so it becomes necessary to take a different sample for screening.

Field Sobriety Tests

In a field sobriety test, the officer gauges your ability to perform certain tasks related to the skills needed to operate a car safely. There are three FSTs that have been standardized, meaning that an officer administering them must follow formal guidelines for the results to be valid:

  • One-leg stand test
  • Horizontal gaze nystagmus test
  • Walk-and-turn test

However, there is no law restricting officers from using field sobriety tests that are not standardized. An unstandardized test that is nevertheless frequently used is the Romberg balance test. It requires you to tilt your head back with your feet together and see if you can maintain your balance while estimating when 30 seconds have elapsed.

The potential problem with field sobriety tests is that if you have an underlying neurological condition, it may cause you to fail the test regardless of your state of intoxication.

DRE Evaluation

If these results are inconclusive, the arresting officer may call in a Drug Recognition Expert, who conducts a more detailed evaluation. This may involve checking your vital signs, inspecting your eyes and nose, and testing your muscle tone for evidence that you have used drugs other than alcohol.

Law enforcement officers must comply with the law while carrying out these evaluations. Contact a Civic Center San Francisco DUI lawyer, like from Hallinan Law Firm, if you suspect that an officer overstepped his or her authority. You may be able to challenge the legality of the arrest.